Selected Balance Sheet Components - Schedule of property and equipment, net (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Property and equipment, net:
Total property and equipment, gross		$ 13,411
Financing right-of-use lease	$ 148
Total property and equipment, gross	16,364
Less accumulated depreciation	(9,220)
Property, Plant, and Equipment and Finance Lease Right-of-Use Asset, after Accumulated Depreciation and Amortization	7,144
Less accumulated depreciation		(7,505)
Property and Equipment		5,906
Depreciation expense	1,700	1,400	$ 1,600
Machinery and equipment
Property and equipment, net:
Total property and equipment, gross	3,152	1,536
Furniture, fixtures and office equipment
Property and equipment, net:
Total property and equipment, gross	775	775
Computer equipment and software
Property and equipment, net:
Total property and equipment, gross	6,174	3,712
Leasehold improvements
Property and equipment, net:
Total property and equipment, gross	5,256	4,587
Construction in process
Property and equipment, net:
Total property and equipment, gross	$ 859	$ 2,801